1. Field of the Invention
The present disclosure generally relates to a display device, and more particularly to a liquid crystal display (LCD) device including a photo-alignment film and a method for manufacturing the same.
2. Description of the Related Art
Unlike twisted nematic (TN) liquid crystal displays, in in-plane-switching (IPS) liquid crystal displays, the electrodes for generating electrical fields to control the liquid crystal (LC) are on a single substrate in the form of strip electrodes. With this electrode arrangement, electric field-induced molecular reorientation occurs mainly in the horizontal direction, providing much lower viewing angle dependence than in TN and vertical alignment (VA) LCD devices. Further, LCD devices having the fringe-field-switching (FFS) mode, which is a more advanced version of the IPS technology, have narrower electrode width and gap so that the areas above the electrodes can also contribute to the switching process.
Positive dielectric anisotropy LC has been commonly used in both IPS mode and FFS mode LCD devices. However, most IPS mode and FFS mode LCD devices have a structure in which the distance between the pixel electrode and common electrode is greater than the cell gap. In such a configuration, strong vertical electric fields tend to form above the electrode surfaces. When the positive type liquid crystal is used, such vertical electric fields can cause tilt rather than twist of the liquid crystal material, leading to insufficient phase retardation. This can severely hamper the peak light transmittance at a certain frame, which in turn causes an asymmetrical brightness between the frames.
Recently, it has been found that employing negative dielectric anisotropy LC in the FFS mode LCD device has several advantages over the positive dielectric anisotropy LC, such as higher transmittance, single gamma curve, lower cell gap dependence and weaker flexo-electric effect. Nevertheless, several technical challenges remain in perfecting the use of negative dielectric anisotropy LC in the LCD devices.